1. Field of the Invention
The weld nut has a series of projections contacting the metal work piece, for the weld to hold the required amount of force, the orientation of the weld nut must be correct with respect to the material that it is being welded to. When welded in the incorrect orientation, and weld nut will fail prematurely and separate from the material welded to.
2. Background Art
There are many different ways to overcome the condition of preventing the welding of upside down weld nuts. The two sided nut solves the issue very simply as it can not be loaded incorrectly. It has projections on both sides of the nut. It is also more expensive to produce and purchase than conventional weld nuts. This method can allow parts to be welded with no weld nut present.
The use of fiber optics to determine the orientation of the weld nuts is another method, but the system must be calibrated as the electrodes wear. This system measures the height difference of the loaded nut. Another limitation is that when using fiber optics, you can only use one controller per set of electrodes.
By using pressurized air through the upper electrode set to a predetermined flow rate, the U.S. Pat. No. 6,303,893 to Perks found that the weld nut orientation could be determined. This design uses customized electrodes and controls that add to the cost to produce and maintain the system. When the upper electrodes begin to wear, the flow rate changes beyond the set values. Either the electrodes are replaced, or the system must be calibrated to account for the additional wear.
Objects and Advantages
Accordingly, besides the object and advantages of the weld nut orientation detection described in my above patent, several objects and advantages of the present invention are:    a) Prevent the welder from welding if no weld nut is loaded;    b) Maintain a consistent welding process by not requiring calibration during the production operation;    c) Maintain consistent process control by being able to use reconditioned electrodes using the same control settings;    d) One detection device can be used to detect weld nuts on multiple sets of electrodes;    e) Utilizes electrodes that are commonly available;    f) The lower electrode wears less due to the greater surface contact as compared to the upper electrode;    g) When electrodes are replaced the control program needs no modification;    h) Utilizes inexpensive controls by using a programmable switch.